pinctrl: rockchip: Add pinctrl support for PX30

There are 4 banks (GPIO0 ~ GPIO3), bank0 is in PD_PMU
subsystem, bank1/bank2/bank3 are in PD_BUS subsystem.

Signed-off-by: David Wu <david.wu@rock-chips.com>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>